Is this possible?

1. ZK prove set of casts that contain tips
2. Tip casts reduced to simple data structure and submitted onchain with proof from step 1
3. Smart contract verifies proof before taking additional actions based on the tip data (ex: updating balances)

sounds like for the circuit part you want to do some kind of regex match on cast text and verify the signature?

would recommend looking in zkemail. it does the same thing for email headers and DKIM signatures

Exactly - yea I found that repo last night. 🙏